Methods for detecting oil deterioration and oil level

ABSTRACT

Methods for detecting oil conditions including a top oil level in an oil system which is reduced to a top level of a threshold amount of the oil, a normal oil deterioration which occurs in the absence of water having a confirmed remaining oil usage, and an abnormal oil deterioration which occurs in the presence of water. The methods comprise a first preferred embodiment which applies a reference and sensing capacitors to obtain a measured temperature compensated electrical property of an oil in use. From which a quantitatively measured remaining usage is obtained so as to a predicted one for the oil. Therefore, the respective top oil level, or the normal or the abnormal oil deterioration can be concluded according to the measured remaining usage which is respectively larger than, or similar to, or less than the predicted one for the oil. A second preferred embodiment only includes the sensing capacitor for obtaining the measured property of the oil. Variations to the embodiments lead to employment of at least two sensing capacitors to monitor an uneven distribution of the oil deterioration or a full range of the oil level of the entire oil system.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention is generally related to oil which is used in machinery such as internal combustion engines and electrical transformers, and more particularly related to methods for the on-line detection of the oil level, and the oil deterioration which occurs in the presence or absence of water.

2. Description of the Prior Art

Devices and methods for detecting oil deterioration and oil level are well known. The following 20 patents and published patent applications are the closest prior art references which are related to the present invention.

1. U.S. Pat. No. 4,517,547 issued to Gary et al. on May 14, 1985 for “Water-In-Fuel Sensor Circuit And Method” (hereafter the “Gary patent”);

2. U.S. Pat. No. 4,646,070 issued to Yasuhara et al. on Feb. 24, 1987 for “Oil Deterioration Detector Method And Apparatus” (hereafter the “Yasuhara patent”);

3. U.S. Pat. No. 4,764,258 issued to Kauffman on Aug. 16, 1988 for “Method For Evaluating The Remaining Useful Life Of A Hydrocarbon Oil” (hereafter the “Kauffman patent”);

4. U.S. Pat. No. 5,540,086 issued to Park et al. on Jul. 30, 1996 for “Oil Deterioration Sensor” (hereafter the “Park First patent”);

5. U.S. Pat. No. 5,929,754 issued to Park, et al. on Jul. 27, 1999 for “High Sensitivity Capacitive Oil Deterioration and Level Sensor” (hereafter the “Park Second patent”);

6. U.S. Pat. No. 6,297,733 issued to Park, et al. on Oct. 2, 2001 for “Stable, Reliable Capacitive Oil Deterioration And Level Sensor” (hereafter the “Park Third patent”);

7. U.S. Pat. No. 5,377,531 issued to Gomn on Jan. 3, 1995 for “Portable Oil Change Analyzer” (hereafter the “Gomn patent”);

8. U.S. Pat. No. 4,733,556 issued to Meitzler et al. on Mar. 29, 1988 for “Method And Apparatus For Sensing The Condition of Lubricating Oil In An Internal Combustion Engine” (hereafter the “Meitzler patent”);

9. U.S. Pat. No. 6,278,282 issued to Marszalek on Aug. 21, 2001 for “Method And System For Determining Oil Quality” (hereafter the “Marszalek patent”);

10. U.S. Pat. No. 6,590,402 issued to Wang et al. on Jul. 8, 2003 for “Engine Oil Condition Sensor” (hereafter the “Wang First patent”);

11. U.S. Pat. No. 6,535,001 issued to Wang on Mar. 18, 2003 for “Method and device For Sensing Oil Condition” (hereafter the “Wang Second patent”);

12. U.S. Pat. No. 6,577,112 issued to Lvovich et al. on Jun. 10, 2003 for “Method And Apparatus For On-Line Monitoring Of Quality And/Or Condition of High Resistive Fluids” (hereafter the “Lvovich patent”);

13. U.S. Pat. No. 7,143,867 issued to Chopra on Dec. 5, 2006 for “Electronic Oil Level Detection And Replacement System” (hereafter the “Chopra patent”);

14. United States Patent Application Publication No.: 2006/0232267 issued to Halalay et al. on Oct. 19, 2006 for “Determining Quality Of Lubricating Oils In Use” (hereafter the “Halalay Publication”);

15. U.S. Pat. No. 6,718,819 issued to Schoess on Apr. 13, 2004 for “Oil Quality Sensor System, Method and Appatus” (hereafter the “Schoess patent”);

16. U.S. Pat. No. 6,278,281 issued to Bauer et al. on Aug. 21, 2001 for “Fluid Condition Monitor” (hereafter the “Bauer patent”);

17. U.S. Pat. No. 6,014,894 issued to Herron on Jan. 18, 2000 for “Motor Sensor System” (hereafter the “Herron patent”);

18. U.S. Pat. No. 6,917,865 issued to Arai et al. on Jul. 12, 2005 for “Engine Oil, Degradation-Determining System And Method, And Engine Control Unit” (hereafter the “Arai patent”);

19. United States Patent Application Publication No.: 2006/0114007 issued to Cho on Jun. 1, 2006 for “Apparatus, A method, And Measuring Sensors For Scanning States Of Engine Oil” (hereafter the “Cho patent”); and 20. China Patent Application Publication No.: 03140986.5 issued to Sun on Dec. 3, 2003 for “Methods For Detecting Deterioration In Oil” (hereafter the “Sun Publication”).

The Gary patent discloses an invention of a water-in-fuel sensor circuit and method. The invention includes a reference capacitor coupled in parallel with a variable capacitor which is immersed in a fuel of a fuel tank, wherein two capacitors are alternately charged and discharged by an oscillator. Water in the fuel will cause increase of the effective capacitance value of the variable capacitor which reduces the absolute magnitude of the current that is detected. The absolute magnitude of the detected current can be utilized to indicate excessive water levels in the fuel.

The Yasuhara patent illustrates an oil deterioration sensor and method. The oil deterioration sensor is comprised of a voltage divider which is constructed by a sensor capacitor and a fixed capacitor, wherein a constant frequency AC voltage source is applied to the voltage divider. Therefore a developed voltage across the sensor capacitor corresponds to the dielectric constant of the lubrication oil, from which the oil deterioration can be detected. The frequency of the AC voltage ranges from 50 KHz to 500 KHz.

The Kauffman patent discloses a method for evaluating the remaining useful life of a hydrocarbon oil containing at least one additive species. A voltammetric analysis is applied to test the remaining amount of the additive, which results in amount of the redox current corresponding to the remaining amount of the additive species. Therefore, the remaining useful life can be concluded in accordance with the magnitude of the current.

The Park First patent discloses an oil deterioration sensor. The sensor includes an oil deterioration sensor capacitor which is constructed with two metal plates, and a total reference capacitor which includes an external fixed reference capacitor. The respective capacitances of the oil deterioration capacitor and the total reference capacitor provide an engine oil deterioration indication for the oil deposited within a gap of the metal plates. The oil deterioration sensor further includes a temperature sensitive resistor thermally connected to a substrate of the sensor for providing a temperature adjustment to the engine oil deterioration indication, and a circuitry utilizing the capacitance of the respective oil deterioration sensor capacitor and the total reference capacitor to generate the engine oil deterioration indication.

The Park Second patent discloses a combination of a capacitive oil deterioration and oil level sensor. The sensor comprises a conductive cylindrical housing member that includes a conductive shielding member defining a ground electrode, and a conductive inner member defining a measuring electrode. The sensor also includes electronics adapted to generate signals indicative to the deterioration of the oil deposited within a gap of two electrodes and a level of the oil along the length of the cylindrically shaped sensor. The oil level is monitored from detecting a ratio of the capacitance of oil dielectric constant over the capacitance of the oil level as C_(∈)/C_(L).

The Park third patent discloses a sensor which has a similar main structure as the sensor of the Park Second patent. In addition, the patented sensor applies electronics including at least one isolating capacitor to eliminate a flow of current between two electrodes that may cause a build up of material on the two electrodes that define the capacitor. This build up of unwanted material may cause an undesirable effect in the sensor output signal. The Park Third patent further discloses the capacitance C_(∈)of the oil deterioration and level sensor capacitor is proportional to ∈ times L, where ∈ is the dielectric constant of the oil and L is the length of the inner electrode. Therefor, the oil level affects the length of the inner electrode, which also affects the capacitance of the sensor.

The Gomm patent discloses a portable oil change analyzer for a laboratory oil test, which is comprised of a viscosity analyzer and a contamination analyzer. The contamination analyzer is based on an optical mechanism, where increase of contaminates in oil results in decrease of a light intensity for an incident light after passing through the oil sample. The oil quality is determined by results from both viscosity and contamination tests.

The Meitzler patent discloses an oil deterioration sensing system comprising an identical reference capacitor and sampling capacitor immersed in the respective fresh oil and sample oil under test. The system tests change of responded frequencies of the tested oil when both capacitors are under excitation of applied frequencies. Results of the test indicates change of the responded frequencies is consistent with change of the viscosity of the oil which is related to the aging of the oil.

The Marszalek patent discloses a method for detecting quality of lubricating oil, which includes a sensor having two electrodes. The method includes applying a potential of a first amplitude to the electrodes immersed in an oil in use, testing a first voltage phase lag, increasing amplitude of the potential to a second amplitude, testing a second voltage phase lag. Therefor, the patented invention can determine the quality of the oil based on the voltage phase lags.

The Wang First patent discloses a method of detecting engine oil if it is contaminated by presence of antifreeze. The method includes applying a series of different voltages to a sensor immersed in an oil in use, testing a corresponded series of the current sensor output voltages, determining a voltage difference between each of the current sensor output voltage relative to a reference voltage. Thereby determining if presenting the antifreeze in the oil after comparing the voltage differences.

The Wang Second patent discloses a device for testing oil condition including an oil condition sensor having electrodes. The electrodes are separated by a gap that is filled with an engine oil. A processor connected to the sensor can be used to determine if the oil is at a first, second and third stage of oil degradation, which is corresponding to a first, second and third sensor output signal trend.

The Lvovich patent discloses an apparatus and a method for monitoring a highly electrically resistive fluid. The method includes applying an AC signal that comprises at least two different AC electrical potentials, with at least one AC potential having a none-zero DC offset, measuring the fluid's electrical response including impedance and its real and imaginary components, thereby determining the fluid quality.

The Chopra patent discloses an invention of electronic oil level and replacement system. The invention is based on the physical phenomenon that a position of a float member is dependent upon an level of the oil. Therefore, a change of the vertical position of the float member will cause a motion of a piston which opens or stops a passage to an oil reservoir. Therefore, the replacement system can work. Following the same mechanism, another float member can activate a lower oil level electric switch or an upper oil electric switch according to the respective oil level, so that the oil level can be electrically detected.

The Halalay patent illustrates a method to detect a change of oil resistivity over a period of elapsed times for an oil in use, which is consistent with to a change of the oil viscosity over the time. Therefore, the method can be applied to monitor oil deterioration including a remaining useful life of the oil.

The Schoess patent discloses an apparatus for determining condition of the engine lubricating oil. The apparatus includes a sensor have a plurality of spaced apart electrode pairs on a nonconductive polymer film. A forcing-function waveform reactive circuit is applied to the sensor input electrode as a common voltage potential. The output current of the sensor output electrode is converted to an equivalent voltage. Based on the voltage values, the sensing apparatus will determine the oil's condition, and will therefore trigger a trouble code if the equivalent voltage falls within a predetermined range.

The Bauer patent discloses a fluid condition monitor, comprising a capacitive spaced array electrode probe which is immersed in the fluid and is applied by an oscillating voltage. A first frequency of at least one hertz is applied and a corresponded first current of the electrode probe is measured. A second frequency is then applied and a corresponded second current is measured. Therefore a difference between the first and second current can be obtained, which can be used to predicated the fluid condition, as compared with a predetermined threshold value.

The Herron patent discloses a motor sensor system for detecting the presence of water in a sealed oil chamber of an engine. The sensor system includes a plurality of flat conductive and insulative annular rings which are alternatively sandwiched together to be an assembly. The assembly is mounted on the propeller shaft in the sealed oil chamber of an engine. Each conductive ring is connected to a remote alarm circuit. In addition, the ring includes a plurality of radially inwardly extending probe sections which are circumferentially spaced around the propeller shift. Thus, if water enters the engine in running, a mixture of the oil and water spans one or more of the gaps formed between the complementary probe sections of the conductive element. Therefore, it completes the alarm circuit and provides an operator of the engine a warning of the water in the oil of the engine.

The Arai patent discloses an engine oil degradation-determining system. The system applies a crankshaft angle sensor which detects the engine rotation speed of an internal combustion engine. Therefore, an electronic device calculates a cumulative revolution number indicative of a degradation degree of the engine oil. An oil level sensor detects an oil level of the engine oil, which is comprised of an upper limit switch and a lower limit switch. Basically, the upper switch monitors the oil level when it reaches a predetermined upper limit, and the lower limit switch monitors the oil level when it reaches a predetermined lower limit. Following this detection mechanism, the invention of the oil level sensor enables to monitor the oil level.

The Cho Patent Application Publication relates to an apparatus, a method, and measuring sensors for scanning engine oil of a vehicle. The invention includes a viscosity sensor which predominantly monitors the oil deterioration, and an oil level sensor which monitor the oil level. The oil level sensor in FIG. 8 has an input electrode 106 having a shape of pipe and installed to have an electric current applied thereto, and an oil level electrode 105 having a shape of a pipe installed apart from the inner surface of the input electrode 106 so as to receive the electric current from the input electrode 106. Therefore, the oil level is calculated on the basis of the capacitance and dielectric constant measured between the oil level electrode 105 and the input electrode 106.

The Sun Patent Application Publication discloses methods for detecting deterioration in oil, comprising a preferred embodiment having a reference and a sensing capacitor. Therefore, variations of electrical properties of the sensing capacitor, which are caused by the temperature variations, can be compensated by the same variations of electrical properties of the reference capacitor. This results in a temperature compensated electrical property of the sensing capacitor, which represents the oil deterioration. Following the same procedure a predicted temperature compensated electrical property profile for the used oil can be established including the property of the respective new oil and spent oil. The profile corresponds to a usage interval having usage of the respective new and spent oil. Therefore, a remaining usage ratio R can be calculated according to the obtained temperature compensated electrical property of the used oil, thereby to determine the remaining usage of the used oil as R times the usage interval. In addition, various methods are disclosed to detect presence of water in oil.

There is a significant need to have methods for detecting oil conditions including a top level of an oil system which is reduced to a top level of a threshold amount of the oil, and oil deterioration which occurs in the absence or presence of the water, to significantly improve usage of the oil and protect machines which use the oil.

SUMMARY OF THE INVENTION

The present invention methods are directed to detect oil conditions including oil deterioration, oil level and a remaining usage of an oil. These conditions are critic for maintaining, thus protecting a machine which uses the oil, such as internal combustion engines and electrical transformers. The oil deterioration can be occasioned by factors such as the thermo-oxidative breakdown, additive depletion, water contamination, breakdown product polymerization, and carbon particulates which are produced in the combustion process. During its deterioration, the oil in use is usually consumed so that a top level of the oil is reduced. The methods of the present invention employ a sensing capacitor which is immersed in the oil and positioned aligning with a predetermined level of a threshold amount of the oil. Therefore, the oil deterioration or top level of the predetermined threshold amount of the oil can be determined from measuring one of various electrical properties of the capacitor.

In a situation during the oil deterioration when the amount of the oil is not significantly reduced so that the capacitor is still fully immersed in the oil, the electrical property of the capacitor is influenced by increase of the dielectric constant of the oil due to progress of the oil deterioration, or by significant increase of the dielectric constant due to presence of water in the oil. In another situation when the amount of the oil is significantly reduced to the predetermined threshold amount, it causes a lower top oil level, which is insufficient for the sensing capacitor being fully immersed in the oil, so that the capacitor is partially filled with the air. According to this condition, the electrical property of the capacitor is predominantly influenced by the dielectric constant of the air which is substantially smaller than the oil dielectric constant.

In accordance with a first preferred embodiment of the present invention methods, a reference capacitor is also used in addition to the sensing capacitor. The reference capacitor is immersed in a reference oil including a dry new oil or a dry spent oil or a dry partially spent oil having the same thermal properties as those of the oil in use. The reference oil and the oil in use are placed in the same temperature environment. In addition, the reference capacitor has defined structural parameters so that the sensing and reference capacitors exhibit the same change of the electrical property according to the oil temperature change when they are immersed into the same oil. In the first preferred embodiment, the electrical properties of the sensing and reference capacitors are combined, thereby eliminating fluctuations of the measured electrical property of the sensing capacitor, where the fluctuations are induced by variations of the oil temperature. Therefore, the preferred embodiment of the present invention enables to obtain a measured temperature compensated electrical property of the sensing capacitor. In this manner, a predicted temperature compensated electrical property profile for the oil also can be simulated, which reflects an entire deterioration for the oil when it is dry.

Applying the measured temperature compensated electrical property, a measured remaining usage of the oil can be obtained from the present invention, so as to a predicted remaining usage for the oil. Comparing the predicted remaining usage for the oil with the measured one, a normal oil deterioration, the oil deterioration which occurs in the absence of the water contamination, can be concluded if the measured remaining usage of the oil is similar to the predicted one. Therefore, the measured remaining usage of the oil can be confirmed as the actual remaining usage, which is useful for a user of the machine to set a schedule of the oil change.

If the measured remaining usage of the oil is apparently shorter than the predicted one, an abnormal oil deterioration, the oil deterioration which occurs in the presence of the water contamination, can be concluded. This conclusion is based on a fact that the dielectric constant of the water is substantially larger than the oil dielectric constant, which causes that the measured temperature compensated electrical property of the sensing capacitor filled with the mixture of the oil and water is different from the predicted electrical property of the same capacitor fully filled with the oil. The difference further leads to a false phenomenon of the shortened measured remaining usage for the oil mixed with the water.

If the measured remaining usage of the oil is noticeably longer than the predicted one, it can conclude that a top level of the oil is reduced to the top level of a predetermined threshold amount of the oil. In this situation, the sensing capacitor which is positioned aligning with the top level of the threshold amount of the oil is partially filled with air due to the lower level of the threshold amount of the oil. The conclusion is based on another fact that the dielectric constant of the air is substantially smaller than the oil dielectric constant. Therefore, the measured property of the capacitor partially filled with the air is different from the predicted property of the same capacitor fully filled with the oil. The difference further leads to a false phenomenon of the prolonged measured remaining usage of the oil.

Obtaining the above illustrated abnormal oil conditions, the user of the machine can taking appropriate actions to protect the machine from damage.

Besides of applying the remaining usage, the first preferred embodiment of the present invention also can conclude that water is likely to be present in the oil if comparing the measured and predicted temperature compensated electrical properties of the sensing capacitor in accordance with following situations:

(a) the measured property EP_(T)(M) exhibits a sudden change which indicates extra deterioration of the oil than the deterioration predicted by the predicted property EP_(T)(P); or

(b) the measured property EP_(T)(M) has a value which differs from the predicted property EP_(T)(P), wherein the difference indicates extra deterioration of the oil than the deterioration predicted by the predicted property EP_(T)(P); or

(c) the measured property EP_(T)(M) has a rate of change of deterioration of the oil which differs from a rate of change of deterioration determined by the predicted property EP_(T)(P), wherein the difference indicates extra deterioration of the oil than the deterioration predicted by the predicted property EP_(T)(P); or

(d) the measured property EP_(T)(M) has a value which exceeds a predetermined extreme value of the predicted property EP_(T)(P), wherein the predetermined extreme value is exceeded at a measurement time which is earlier than a time predicted by the predicted property profile; or

(e) the measured property exhibits an initial anomaly which shows extra deterioration of the oil than the deterioration determined by the predicted property, and then returns to the normal value, when starting a cold internal combustion engine.

From comparing the measured and predicted temperature compensated electrical properties of the capacitor, the first preferred embodiment of the present invention further can conclude that the top level of the oil is reduced to a top level of the threshold amount of the oil if the measured electrical property differs from the predicted electrical property, where the difference indicates less deterioration of the oil than the deterioration determined by the predicted property.

The present invention also discloses variations of the first preferred embodiment, which comprise at least two sensing capacitors. The at least two sensing capacitors can be placed to different locations of an oil system of the machine so that the user of the machine can determine if there is an uneven distribution of the oil deterioration through the entire oil system. This information is particularly useful for a large size internal combustion engine such as one equipped to a locomotive or ship, where water can exist in particular locations of the oil system. If the at least two sensing capacitors can be positioned along a vertical orientation, a change of a full range of the oil level can be monitored when the oil amount is gradually consumed so as to gradually lower the top oil level. Accordingly, each of the at least two sensing capacitors will change sequentially from a capacitor filled with the oil to one filled with air. Therefore, an in situ oil top level can be monitored from detecting such sequential change of the respective electrical property of the respective each of the at least two sensing capacitor.

In accordance with a second preferred embodiment, the present invention only applies the sensing capacitor. A measured temperature compensated electrical property of the capacitor can be obtained so as to a predicted property profile, according to a number of known temperature compensation methods. Under this situation, the second embodiment further enables to derive the measured remaining usage of the oil. Therefore, the second embodiment of the present invention can determine oil conditions including a top oil level which is reduced to a top level of the threshold amount of the oil during the oil reduction process, the abnormal oil deterioration and normal oil deterioration including a confirmed remaining usage of the oil, following the same strategy of comparing the measured remaining usage with the predict one. In addition, the second embodiment further enables to apply at least two sensing capacitor for monitoring if there is the uneven distribution of the oil deterioration or a change of a full range of the oil level of the oil system in the machine.

It is therefore an object of the present invention to obtain a temperature compensated electrical property of a sensing capacitor from applying a reference capacitor, so that variations of the electrical property of the sensing capacitor, which are induced by the temperature variations, can be compensated by the same variations of the property of the reference capacitor.

It is also an object of the present invention to quantitatively describe deterioration of an oil in use from establishing a predicted temperature compensated electrical property profile with applying a dry new oil or a dry partially spent oil or a dry spent oil having respective known usages, so that an oil under measurement can be determined for its deterioration, from comparing the measured temperature compensated electrical property of the oil with a corresponded property of the predicted property profile.

It is also a further object of the present invention to quantitatively describe a remaining usage of an oil from establishing a measured remaining usage ratio as R_(M)=[EP_(T)(M)−EP_(T,S)]/[EP_(T,N)−EP_(T,S)], which leads to a measured remaining usage as R_(M) ΔU_(F)=R_(M)×(U_(S)−U_(N)), and corresponded predicted remaining ratio and remaining usage in a similar fashion, if there is a linear relationship between the temperature compensated electrical property of the oil and the usage of the oil.

It is also another object of the present invention to quantitatively describe a remaining usage of an oil from establishing a measured remaining usage as ΔU_(M)=(U_(S)−U_(M)), and corresponded predicted remaining usage in a similar fashion, if there is non linear relationship between the temperature compensated electrical property of the oil and the usage of the oil.

It is a further object of the present invention to compare if the measured remaining usage is respective shorter than, similar to and longer than the predicted remaining usage, so that the present invention can conclude the oil conditions including the respective abnormal oil deterioration, normal oil deterioration, and a top oil level which is reduced to the top level of a predetermined threshold amount of the oil.

It is additional object of the present invention to apply at least two measurement sensors which are positioned at different locations through an entire oil system, so that the present invention enables to determine if there is an uneven distribution of the deterioration of the oil including if water is accumulated to specific locations in the oil system.

It is a further additional object of the present invention to apply at least two measurement sensors which are positioned at different levels of the oil system, wherein the first of the at least two sensors is positioned whose sensing capacitor is aligned with a level that is adjacent and below a top level of the oil which is newly replaced, and second of the at least two sensor is positioned whose sensing capacitor is aligned with the top level of a threshold amount of the oil, so that a detailed information can be obtained for reduction of the top level of the oil in the oil system.

Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring particularly to the drawings for the purpose of illustration only and not limitation, there is illustrated

FIG. 1 is a graph showing deterioration of an oil in use as the function of time;

FIG. 2 is a graph showing decrease of impedance of the oil as the function of increase of the elapsed times according to the oil deterioration illustrated in FIG. 1;

FIG. 3 is a graph showing relationship between a measured impedance profile Z_(M) and a temperature compensated impedance profile Z_(T);

FIG. 4 is a graph showing a predicted temperature compensated impedance profile Z_(p), which is consistent with the actual temperature compensated impedance profile Z_(T);

FIG. 5 is a circuit diagram showing an impedance measurement using a voltage divider;

FIG. 6 is a circuit diagram showing a current measurement using a constant voltage source;

FIG. 7 is a circuit diagram showing a voltage measurement using a constant current source;

FIG. 8 is a graph showing profiles of the impedance (Z), voltage (V), and current (I) for an oil deteriorating over the time;

FIG. 9 is a diagram of an apparatus from a first preferred embodiment of the present invention where a temperature compensated electrical property is developed;

FIG. 10 is a graph which shows an electrical property profile of the respective sensing capacitor and reference capacitor without the temperature compensation;

FIG. 11 is a graph which shows a measured temperature compensated electrical property profile EP_(T)(M) of the sensing capacitor as derived from FIG. 10;

FIG. 12 is a second graph to illustrate an electrical property profile of the respective sensing capacitor and reference capacitor without temperature compensation;

FIG. 13 is a graph showing a measured and predicted temperature compensated electrical property profiles during a normal deterioration of the oil, where the profiles are presented in accordance with the independent variable of the elapsed times;

FIG. 14 is a graph showing the same measured and predicted temperature compensated electrical property profiles during a normal deterioration of the oil of FIG. 13. However, the profiles are presented according to the independent variable of usage of the oil which includes the used times or the traveled miles;

FIG. 15 is a graph showing the same curves in FIG. 14 including the predicted temperature compensated electrical property profile and a measured temperature compensated electrical property profile according to the usage of the oil. The difference is that the measured property staring at the moment “U_(i)” has a sudden change, which illustrates extra deterioration of the oil than it should be;

FIG. 16 is a graph which magnifies a section of the profile of the measured property in FIG. 15 which has the sudden change at the moment “U_(i)”, wherein the independent variable is presented as the time “t”;

FIG. 17 is a graph which shows that a measured temperature compensated electrical property during the time period of t_(i) and t_(j) has a steeper slope than the slope of the predicated property;

FIG. 18 is a graph showing a measured temperature compensated electrical property profile which exceeds a predetermined extreme value of the predicted temperature compensated electrical property before it should be;

FIG. 19 is a graph showing a measured temperature compensated electrical property in a cold internal combustion engine which exhibits an initial anomaly of extra oil deterioration;

FIG. 20 is a diagram of a second apparatus of the present invention for detecting the oil deterioration and oil level;

FIG. 21 is a graph which shows the same curves in FIG. 14. The difference in FIG. 21 is that the measured property starting from the moment “U_(i)” is different from the predicted property, which indicates less oil deterioration than it should be;

FIG. 22 is a graph which magnifies a section of the measured and predicted profiles which appears during a period of the usage U_(i) to U_(q) of FIG. 21;

FIG. 23 is a diagram of an apparatus from a variation of the first preferred embodiment of the present invention wherein at least two measurement sensors are applied to position at different locations of an oil system; and

FIG. 24 is a diagram of an apparatus from another variation of the first preferred embodiment of the present invention wherein at least two measurement sensors are applied for positioning at different levels of an oil system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although specific embodiments of the present invention will now be described with reference to the drawings, it should be understood that such embodiments are by way of example only and merely illustrative of but a small number of the many possible specific embodiments which can represent applications of the principles of the present invention. Various changes and modifications obvious to one skilled in the art to which the present invention pertains are deemed to be within the spirit, scope and contemplation of the present invention as further defined in the appended claims.

Oil conditions are critic for maintaining, thus protecting a machine which uses an oil. The conditions include abnormal deterioration of the oil which occurs in the presence of water, or normal deterioration of the oil which occurs in the absence of water and contains a remaining usage of the oil that is useful for a schedule to change the oil, and a top level of the oil in the machine when it is reduced to a top level of a threshold amount of the oil. The present invention methods are aimed to detect these conditions from applying a single measurement sensor, thereby providing respective indications to a user of the machine for taking appropriate actions to protect the machine from damage. The methods are disclosed in the following two sections.

I. Methods for Detecting Deterioration of an Oil

In a machine such as an internal combustion engine, lubricating oil is used to reduce friction between moving engine parts. Over time however the oil deteriorates and is therefore less effective in protecting the engine from damage. The life span of the oil is limited by factors such as the thermo-oxidative breakdown, additive depletion, water contamination, breakdown product polymerization, and carbon particulates which are produced in combustion of the engine operation.

Within the above mentioned facts, the water contamination effects differently, as compared with the rest of facts to effect the oil chemical, physical and electrical properties. Therefore, it will be appreciated that oil deterioration can be classified as the normal one which occurs in the absence of the water and the abnormal one which occurs in the presence of the water. FIG. 1 shows a normal oil deterioration profile (D) according to the elapsed times (t). When an oil is new or unused there is no deterioration, which is shown at a point “D_(N)”. As time progresses and the oil is used, contaminants build up. Eventually, the deterioration reaches a point “D_(S)” when the oil is spent and should be changed.

Similarly, the oil used in power transformers is subject to breakdown. Primary causes for deterioration include heat, oxygen, moisture, and electrical stress: partial discharge and arching.

It is well known that the dielectric constant of the oil increases with increase of the oil contamination and thus deterioration. Therefore, by making use of this property, a degree of the oil deterioration may be measured electrically. This can be done by placing a sensor such as a capacitive probe (C) in the oil and measuring the electrical properties of the oil as manifested by electrical properties of the probe. As contaminants build up the deterioration progressively occurs and the dielectric constant (∈) of the oil increases leading to an increase of the probe's capacitance (C_(p)).

The increase of the capacitance causes a decrease of the impedance (Z) of the oil according to the equation Z=R+j(−1/ωC). The decrease of the impedance in turn increases the current (I) which flows between the plates of the capacitive probe when an AC voltage (V) is applied across the plates. Such technology is well known in the art, and is specifically disclosed in U.S. Pat. No. 4,646,070. FIG. 2 illustrates during the normal oil deterioration a decrease of the impedance (Z) as a function of an increase of the used times of the oil. The impedance value “Z_(N)” is high for the new or unused oil, and the impedance value “Z_(S)” is low for the spent oil. Additionally, since oil is basically non-conductive, the capacitive reactance j(−1ωC) or (X_(c)), a component of the impedance is the predominant factor to govern the value of the impedance. Referring to FIG. 2, it will be appreciated that a user may periodically measure the impedance to determine the quality of the oil (denoted by dots). Measurement may range anywhere from continuous to infrequent.

However, it is noted that values of the dielectric constant of the oil are also influenced by the temperature variations, which cause variations of the capacitance of the capacitor so as to the impedance. Therefore, it is necessary to eliminate this temperature effect in the measurement by “compensating” variations of the measured impedance. This may be done by measuring the temperature of the oil and applying a correction factor to convert the measured impedance value (Z_(M)) to the actual or temperature compensated impedance value (Z_(T)). Also, a temperature compensated measurement can be made by always measuring the oil at a predetermined temperature. FIG. 3 shows relationship between the measured impedance profile (Z_(M)) and the temperature compensated impedance profile (Z_(T)) according to the used times, wherein the time is an independent variable that is expressed as a particular type of the oil usage.

FIG. 4 is a graph showing a predicted temperature compensated impedance profile (Z_(p)) as compared with the actual or measured temperature compensated impedance profile (Z_(T)). The predicted impedance profile (Z_(p)) is anticipated, which decays smoothly as the function of the times. This indicates the normal deterioration of the oil. The predicted curve (Z_(p)) could be developed empirically through test measurements. In the illustrated example, the actual impedance (Z_(T)) closely follows the predicted impedance (Z_(p)). This is a further indication of the normal oil deterioration. However, as it will be discussed later, certain influences can cause the predicted values to differ from the actual values of the impedance.

Referring to FIGS. 2-4, the oil deterioration has been shown in terms of the impedance measurement. Such impedance measurement may be made by placing a sensing capacitor in series with a known impedance to form a voltage divider, and applying an AC voltage across the impedance of the capacitor and the known impedance. The ratio of a voltage across the capacitor to a voltage across the known impedance is proportional to the impedance of the capacitor, which is the representation of the oil impedance.

It will be appreciated however, that the oil deterioration could also be represented and measured in terms of a current (I) flowing through the capacitor as a result of an applied constant voltage, or in terms of a voltage (V) developed across the capacitor as a result of an applied constant current. Any of these measurements may be performed using techniques well known in the electrical art. As in the case of the measured current and voltage they must also be temperature compensated.

Methods of measuring the various electrical properties of the capacitor are shown in FIGS. 5-7. The capacitor (C) can be constructed with two or more metal conductors in parallel having a spaced gap between two adjacent conductors for sufficient oil circulation. FIG. 5 is a circuit diagram which illustrates the impedance measurement using a voltage divider. An alternating voltage source (V_(A)) applies a potential across a capacitor (C) connected to a reference impedance (Z_(ref)) of known value. The impedance of the capacitor (C) represents the deterioration of the oil. In one embodiment, the reference impedance (Z_(ref)) is a resistor.

FIG. 6 is a circuit diagram for the current measurement using a constant voltage source (V₀). The current (I) through the capacitor (C) represents the deterioration of the oil.

FIG. 7 is a circuit diagram for the voltage measurement which uses a constant current source I₀. The voltage (V) across the capacitor C represents the deterioration of the oil.

FIG. 8 is a graph which illustrates profiles of the impedance, voltage, and current of the capacitor filled with an oil which deteriorates according to the elapsed times. It is of course noted that the impedance and voltage will decrease smoothly as the oil deterioration in progress, and that the current will correspondingly increase as development of the oil deterioration.

It will be appreciated that the impedance could be further separated into its imaginary component: capacitive reactance (X_(c)), which is equal to j(−1/ωC), and real component: resistance (R). Therefore, either of these measured components of the impedance, using procedures well known in the art, can provide an indication of the oil deterioration. Such measurements can be made using an impedance analyzer such as an Agilent 4294A to obtain impedance, reactance, resistance, capacitance, and phase angle. It is noted that phase angle can be determined by resistance and reactance.

Now referring to FIGS. 9-11, there is illustrated a method in accordance with a first preferred embodiment of the present invention for detecting oil conditions including a top level of the predetermined threshold amount of the oil, or abnormal deterioration of the oil which occurs in the presence of the water, or normal deterioration of the oil which occurs in the absence of the water and contains a remaining usage of the oil. In this embodiment, a reference sensor is utilized to compensate variations of the measured electrical property, which are induced by the temperature variations. The method includes:

(a) providing an oil 22 in use which is disposed in an oil system including an oil reservoir of a machine such as a crankcase 34 of an engine or a container of an electrical transformer;

(b) providing a reference oil 24 disposed in a sealed container which is located in a common temperature environment with the oil 22. The reference oil 24 is free of water;

In the preferred embodiment, the reference oil 24 has the same thermal properties as the oil 22. That is, temperature variations cause the electrical properties of the reference oil 24 and the electrical properties of the oil 22 to change in a like manner. Also in the preferred embodiment, the reference oil can be either (1) an unused oil, or (2) a spent oil, or (3) a partially spent oil. For example, the reference oil 24 which is illustrated in FIG. 10 is the unused oil of the same brand and type as the oil 22.

(c) providing a measurement sensor 26 which includes a first capacitor (C1) as a sensing capacitor;

In the preferred embodiment, the measurement sensor 26 may further include a container which has a plurality of openings for allowing oil circulation in addition to protect the sensing capacitor placed inside of the container. Therefore the container of the sensor is represented to be the dashed lines in FIG. 9.

(d) providing a reference sensor 28 which includes a second capacitor (C2) as a reference capacitor. The reference sensor 28 includes the sealed container wherein the reference capacitor (C2) is fully immersed in the reference oil 24.

In a preferred embodiment on their related structural parameters, the first and second capacitors should both exhibit the same change in the electrical properties according to the oil temperature change when they are immersed into the same oil. Also, it will be appreciated that the measurement sensor 26 and reference sensor 28 can be arranged into an integrated mechanical unit.

(e) positioning the measurement sensor 26 to the oil system wherein the sensing capacitor (C1) is fully immersed in the oil 22;

(f) measuring an electrical property EP_(C1) and EP_(C2) of the respective first capacitor (C1) and the second capacitor (C2), wherein the electrical property is one of:

-   -   the impedance of the respective first capacitor and second         capacitor;     -   the current passing through the respective first capacitor and         second capacitor;     -   the voltage developed across the respective first capacitor and         second capacitors;

(g) combining the electrical property of the first capacitor (EP_(C1)) with the electrical property of the second capacitor (EP_(C2)) to obtain a measured temperature compensated electrical property EP_(T)(M) of the sensing capacitor, which represents a measured temperature compensated electrical property EP_(T)(M) of the oil. This oil property may represent deterioration of the oil 22; Here the symbol “EP_(T)(M)” is used to represent the property of the oil, where the subscribed letter “T” indicates the temperature compensation, and the letter “M” means the electrical property “EP” which is obtained through measurement.

Referring to FIG. 9, the electrical properties (EP_(C1)) of the first capacitor and the electrical property (EP_(C2)) of the second capacitor are combined in a measurement device 30 to result in the measured temperature compensated electrical property EP_(T)(M) of the sensing capacitor, which can be routed to a display 32 for presentation to the user under the user's choice.

Referring now to FIGS. 10 and 11, there is illustrated how the variations of the electrical property (EP_(C1)) can be compensated by applying the reference capacitor (C2) from the present invention. In this embodiment, the reference oil is the unused oil or the new oil of the same brand and type as the oil 22. As illustrated, during the time interval (Δt₁), the electrical property (EP_(C2)) of the second or reference capacitor has a constant value (EP_(C2)N). However, during the time period (Δt₂) the value (EP_(C2)) increases due to a change of the oil temperature. Similarly, during the time interval (Δt₃) the value returns to the normal one, and during the time period (Δt₄) the value again increases due to a temperature change. In addition, it will be appreciated that the reference oil is sealed separately, so that it is not subject to conditions caused by operation of the machine, and thus it does not deteriorate during the entire life of its usage. This is illustrated by its vale (EP_(C2)N) that is unchanged over the times, wherein (EP_(C2)N) is a normal value of the electrical property of the second capacitor filled with the new oil.

Such behavior of the electrical property (EP_(C2)) is utilized as a baseline to correct or compensate the electrical property (EP_(C1)) of the first or sensing capacitor filled with the oil, which is also influenced by the temperature variations. In addition, the electrical property of the first capacitor is also influenced by the progress of the oil deterioration according to the oil usage of the elapsed times. Therefore, the oil is changed starting from a new oil when the oil is unused to a spent oil when the oil is completely used. For this reason, the initial property of the first capacitor is the same as (EP_(C2)N) of the second capacitor.

It will be appreciated that the temperature change effects the electrical property (EP_(C1)) and electrical property (EP_(C2)) in an identical fashion since both capacitors are in the same temperature environment, the respective filled oils have the same or similar thermal properties, and the capacitors are constructed by the defined structural parameters. Therefore, by combining electrical property (EP_(C1)) and electrical property (EP_(C2)) according to a below-cited equation [1], the result is a measured temperature compensated electrical property EP_(T)(M) of the sensing capacitor, which may be the representation of the oil deterioration.

It will be appreciated that the shown curve for the electrical property in FIG. 11 is one for the impedance or voltage. If the measured property is the current, the curve would be as that shown in FIG. 8.

Referring to FIG. 11, there is illustrated that the measured electrical properties of capacitors (C1) and (C2) have been combined to result in the measured temperature compensated electrical property EP_(T)(M) at each measurement over the entire life of the oil starting from the new oil which deteriorates to be the spent oil, thereby to form the profile. In a preferred embodiment of combining the electrical properties of the two capacitors, variations of the electrical property (EP_(C1)) of the sensing capacitor (C1) due to the temperature variations is essentially subtracted from the same variations of the electrical property (EP_(C2)) of the reference capacitor (C2) in accordance with the following equation [1]:

EP_(T)(M)=EP_(C1)−EP_(C2)+EP_(C2) N  [1]

From the equation, the value (EP_(C2)N) can be a value including the nominally measured value of EP_(C2), which positions EP_(T)(M) along the positive values of the y axis in FIG. 11. Referring to the figure, the y axis represents the temperature compensated electrical property (EP r) of an oil including the new, partially spent and spent oil. The x axis is each of the elapsed times during deterioration of the oil.

However, it will be another appreciated that other methods of combining (EP_(C1)) and (EP_(C2)) such as (EP_(C1)-EP_(C2)) could also be employed so long as the electrical property (EP_(C2)) of the second or the reference capacitor (C2) is utilized to remove the temperature effects from the electrical property (EP_(C1)) of the first or the sensing capacitor (C1). Further, if combining the properties through (EP_(C2)-EP_(C1)), a deterioration profile of the oil can be obtained, which is similar to the one in FIG. 1.

Also, referring to FIGS. 9-11, and as previously mentioned in step (f) above, the electrical property could be one of the components of the impedance, resistance (R) or capacitive reactance (X_(c)), rather than the total composite impedance. Measurement procedures and equipments well known in the art could be used to make such measurements, for this or other oil measurement methods disclosed herein.

It will be appreciated that as described herein the “unused” oil is a new or fresh oil which is essentially free of contaminants. The “partially spent” oil is an oil that has been in use for some period of time, and therefore has some build up of contaminants. Also, the measured temperature compensated electrical property profile EP_(T)(M) shown in FIG. 11 utilizes the time as the independent variable. However, other parameters besides the time could also be utilized. For example in a motor vehicle the temperature compensated electrical property profile (EP_(T)) could be expressed as the function of a usage of the oil, such as traveled miles rather than the used times.

FIG. 12 illustrates an alternative method for compensation of the temperature effects. In this embodiment the spent oil rather than the unused oil is used as the reference oil. Therefore, the sensing capacitor (C1) is immersed in the oil 22 as before, but the reference capacitor (C2) is immersed in the reference oil 24 which is the spent oil having its normal value (EP_(C2)N′). The spent oil is an oil with large concentrations of contaminants, and therefore whose lubricating properties are effectively exhausted. The spent oil used as the reference oil 24 preferably has the same thermal properties as the oil 22. In the respective time period (Δt₂) and (Δt₄) a same change in oil temperature causes the same increase in both (EP_(C1)) and (EP_(C2)).

It will be appreciated that if the measured electrical properties of capacitors (C1) and (C2) in FIG. 12 have been combined as before, a resulted measured temperature compensated electrical property profile EP_(T)(M) of the sensing capacitor is identical to the property profile EP_(T)(M) shown in FIG. 11. It will be further appreciated that through the later discussions, the above disclosed property EP_(T)(M) can serve as the representation of the oil deterioration or oil level according to the respective situations.

In addition, following the above disclosed steps (a) to (g), it can obtain a predicted temperature compensated electrical property profile EP_(T)(P) for the oil 22, which reflects the progress of the normal deterioration for the oil in its entire life of usage if the oil is dry. The predicted profile includes the electrical property (EP_(T,N)) for a new oil when the oil is new or unused, and an electrical property (EP_(T,S)) for a spent oil when the oil is spent. Between the electrical properties (EP_(T,N)) and (EP_(T,S)), there are various different electrical properties (EP_(T,PS)) for the respective partially spent oils. The electrical properties (EP_(T,PS)) reflect the oil when it is dry at different stages of the oil deterioration according to the respective oil usages.

The predicted property profile for the oil EP_(T)(P) can be obtained from various previously disclosed methods. Hereafter is an example for experimentally simulating the entire deterioration for the oil 22 when it is dry to obtain the predicted property profile EP_(T)(P). When the oil is new or unused which obviously does not contain water, the new oil is tested following the above disclosed steps (a) to (g), which results in the electrical property (EP_(T,N)). Then the dry new oil is experimentally used for a purpose to make it deteriorated according to a predetermined period of the experimental times. It will be appreciated that experimental conditions are the same as or mostly close to conditions of the real usage of the oil. The dry new oil then becomes a partially spent dry oil have a predetermined degree of deterioration which correlates to the experimental times. Then the dry oil having the known degree of deterioration is measured following the above disclosed steps (a) to (g), which results in an electrical property (EP_(T,PS)). The dry oil having the known degree of deterioration is experimentally used for the second time according to the same predetermined period of the experiment times, where all the experimental conditions are kept the same for the entire experiment of oil deterioration. Thus it causes the dry oil further partially deteriorated. Then the further partially deteriorated oil is measured again following the above disclosed steps (a) to (g), which results in a property that reflects a larger degree of the oil deterioration, as compared with the prior property (EP_(T,PS)). Following this manner to complete the oil deterioration, the oil is deteriorated to the spent oil. Therefore, the predicted temperature compensated electrical property profile EP_(T)(P) can be established, which represents the normal oil deterioration that occurs for the oil 22 if it is dry. It will be appreciated that the reference oil also can be applied for obtaining such predicted electrical property profile EP_(T)(P) since the reference oil is a dry oil having the same brand and type as the oil 22, which is disclosed before.

Therefore, the first embodiment of the present invention continually comprises the following step:

(h) following the steps (a) to (g) establishing a predicted temperature compensated electrical property profile for the oil, which reflects the normal oil deterioration, the predicted profile includes an electrical property (EP_(T,N)), which is equal to a measured property EP_(T)(M) of the oil if it is unused and dry, and another electrical property (EP_(T,S)), which is equal to the measured property EP_(T)(M) of the oil if it is spent and dry.

Now the normal oil deterioration, which has been briefly disclosed in FIG. 4, will be illustrated in detail in FIGS. 13 and 14. FIGS. 13 and 14 illustrate the same situation of the normal oil deterioration, where the measured electrical property profile EP_(T)(M) is consistent with the predicted one EP_(T)(P). It will be appreciated that, for a comparison with an abnormal oil deterioration in later discussion, a partial of the measured property profile is presented in the figures.

Referring to FIG. 13, the predicted profile includes the properties of the new oil, spent oil and partially spent oils, which is presented as the dashed line. The partial of the measured profile, which is presented as the solid line, includes the properties of the new oil and the oil in use. The measured property profile EP_(T)(M) illustrates that the new oil has been used thus deteriorated in a period of the times that ends at the time moment (t_(i)), which corresponds to a property EP_(T,i)(M). Accordingly, the predicted property profile of the oil also contains a property EP_(T,i)(P) according to the time moment (t_(i)), wherein the measured property EP_(T,i)(M) has the same value, as compared with the predicted EP_(T,i)(P).

Now referring to FIG. 14, it illustrates the same measured and predicted property profile as disclosed in FIG. 13. However, instead of using the time as the independent variable, FIG. 14 employs the actual usage of the oil (U) as the variable. Therefore, the properties (EP_(T,N)) and (EP_(T,S)) of the respective new and spent oil are related to the respective usages (U_(N)) and (U_(S)). The usage (U_(S)) represents a number of the traveled miles or used times of the spent oil during the entire life of usage of the oil which is changed from the new oil to the spent oil. It will be appreciated that due to the consistency between the predicted and measured properties, the electrical properties of the respective new and spent oil from the both measured and predicted properties are presented as the same respective properties (EP_(T,N)) and (EP_(T,S)). Accordingly, a full range of the oil usage ΔU_(F)=(U_(S)-U_(N)) is defined relative to the electrical property change (EP_(T,N)-EP_(T,S)). In addition, FIG. 14 further illustrates that the measured temperature compensated electrical property EP_(T,i)(M) is consistent with a predicted one EP_(T,i)(P) at the same usage moment (U_(i)), which represents the normal oil deterioration.

Obtaining the above mentioned information, the first embodiment of the present invention continually comprising the following steps:

(i) establishing a full range of usage for the oil as (ΔU_(F))=(U_(S)−U_(N)) according to change of the electrical properties as (EP_(T,N)−EP_(T,S)), wherein usage (U) represents an actual oil usage which is an independent variable to the property (EP_(T)), so that the (U_(N)) is an actual usage of the new oil and the (U_(S)) is the actual usage of the spent oil;

(j) defining a measured normalized remaining usage ratio (R_(M)) of the oil having the property EP_(T)(M) as:

R _(M)=[EP_(T)(M)−EP_(T,S)]/[EP_(T,N)−EP_(T,S)],

wherein (R) is a remaining usage ratio, and ranges from one for the new oil to zero for the spent oil.

(k) defining a measured remaining usage of the oil as R_(M) ΔU_(F)=R_(M)×(U_(S)−U_(N)).

Accordingly, a measured normalized ratio of the oil deterioration (D_(M)) of the oil having the electrical property EP_(T)(M) can be defined as:

D_(M)=[EP_(T,N)−EP_(T)(M)]/[EP_(T,N)−EP_(T,S)], wherein the deterioration ratio (D) ranges from zero for the new oil to one for the spent oil.

In addition, it can be similarly established for a predicated normalized remaining usage ratio (R_(p)), according to a predicted electrical property EP_(T)(P) from the predicted property profile. For example, the predicted property is EP_(T,i)(P) in FIGS. 13 and 14. The predicated remaining usage ratio is R_(p)=[EP_(T)(P)−EP_(T,S)]/[EP_(T,N)−EP_(T,S)], which leads to the predicted remaining usage is (R_(p)ΔU_(F)), and the predicated deterioration ratio is D_(p)=[EP_(T,N)−EP_(T)(P)]/[EP_(T,N)−EP_(T,S)].

According to the illustration of FIG. 14, it will be appreciated that the measured remaining usage ratio (R_(M)) is consistent with the predicted ratio (R_(p)) according to the same usage moment (U_(i)). Therefore the measured remaining usage (R_(M)ΔU_(F)) is also consistent with the predicted remaining usage (R_(p)ΔU_(F)). In this situation, the normal deterioration is concluded to the oil in use, plus the measured remaining usage which is confirmed as the actual remaining usage.

Therefore, continuing from the previous step (k) of the method, the present invention has the following steps to conclude the normal deterioration of the oil which is developed in the absence of the water:

(l) from the predicted property profile, determining a predicted temperature compensated electrical property EP_(T)(P) according to a same usage moment as compared with the measured property EP_(T)(M), establishing a predicated remaining usage ratio as R_(p)=[EP_(T)(P)−EP_(T,S)]/[EP_(T,N)−EP_(T,S)], from which to obtain a predicted remaining usage (R_(p)ΔU_(F));

(m) determining the normal deterioration of the oil which occurs in the absence of water if the measured remaining usage (R_(M)ΔU_(F)) is similar to the predicated remaining usage (R_(p)ΔU_(F)), and confirming the measured remaining usage which represents the actual remaining usage of the oil;

It will be appreciated that the similarity between the measured and predicted remaining usages can always be easily and quantitatively defined by a predefined threshold value in application of the present invention.

It will be further appreciated that the above normalized remaining usage ratio (R_(M)) or (R_(p)) which have been derived according to an approximation of the linear relationship between the change of the electrical property (EP_(T,N)−EP_(T,S)) and the usage range (U_(S)−U_(N)). Therefore, the measured remaining usage (R_(M)ΔU_(F)) is a close approximated value to an actual remaining usage.

It will be additionally appreciated that a normalized remaining usage ratio (R′) also could be mathematically derived, which is based on a possible nonlinear relationship between the change of the electrical property (EP_(T,N)−EP_(T,S)) and the full usage range (U_(S)−U_(N)).

However, despite the shape of the predicted and measured property profiles EP_(T)(P) and EP_(T)(M), the measured actual remaining usage is always correctly presented as: ΔU_(M)=(U_(S)−U_(i)). Referring to FIG. 14, (U_(i)) is the usage of the oil at the measurement point (i), which correlates to the both measured and predicted properties EP_(T,i)(M) and EP_(P,i)(P) during the normal oil deterioration. Therefore, the predicted actual remaining usage is ΔU_(p)=(U_(S)−U_(p)), which is equal to the measured actual remaining usage ΔU_(M)=(U_(S)−U_(M)). This also proves the normal deterioration of the oil, and confirms the measured actual remaining usage.

Now referring to FIG. 14 again, there is illustrated that up until the moment (U_(i)), the predicted property EP_(T)(P) are consistent with the measured property EP_(T)(M). That indicates the oil in use which is deteriorating in a predicted manner. However, as will be subsequently discussed, events occurring at the moment (U_(i)) cause the value of the measured electrical property to differ from the value of the predicted electrical property.

Reference to FIG. 15 illustrates detection of the abnormal deterioration of the oil which occurs in the presence of water, wherein it is at the moment (U_(i)) that the presence of the water happens. As illustrated in FIG. 15, there is a sudden change of the measured property from EP_(T,i)(M) to EP_(T,i,w)(M), as compared with the predicted property EP_(T,i)(P) which represents the normal oil deterioration which occurs in the absence of water. In addition, since the moment (U_(i)), the measured property profile consistently departs from the predicted property profile.

For a detailed illustration, FIG. 16 magnifies a section of the measured property profile according to the moment (U_(i)) when the sudden change of the property occurs. However, the time is used as the independent variable in FIG. 16. In this embodiment, the likely presence of water in the oil is detected. For example, in an internal combustion engine, a head gasket could be partially ruptured at a small scale. An initial presence of the small rupture allows the water suddenly to enter into the oil system, which causes the corresponded sudden change of the measured property. It will be appreciated that the electrical property of the sensing capacitor could possibly be effected by other factors, however the sudden change in electrical property is likely to be the result of the water contamination. This is because that the dielectric constant of the water is significantly larger (approximately 3-4 times) than the dielectric constant of the oil.

The presence of water in the oil will reduce the impedance of the sensing capacitor or the voltage developed across the capacitor, and correspondingly increase the current flowing through the capacitor filled with the mixture of the water and oil. Therefore, the fact of suddenly presenting water in the oil will cause the sudden change of the electrical properties of the sensing capacitor, which are presented as extra deterioration of the oil, as compared with the normal deterioration which is determined by the predicted property.

Referring to FIG. 16 again, there is illustrated that it is at the moment (ti) of the time interval (Δt_(i)), the measured property EP_(T,i)(M) of the impedance or voltage has a sudden drop to a property EP_(T,i,W)(M), wherein the letter (w) denotes the water. As further illustrated, during the rest of the time interval (Δt_(i)), the profile continuously decreases aligning with its initial slope, or the initial pattern of changing the property, which exists prior to the moment (t_(i)). This is because of the continuous presence of a constant small amount of the water due to a dynamic water balance in the oil such as when extra amount of the water could be evaporated.

As compared with FIG. 16 which describes the water presence during the small time interval (Δt_(i)), FIG. 15 particularly illustrates how the presence of water in the oil causes a change of the measured temperature compensated electrical property and the corresponded remaining usage as well, as compared with the respective predicted values.

Referring to FIG. 15 since the moment (U_(i)), the oil mixed with the constant amount of the water exhibits a pattern of the measured property EP_(T)(M) as the same pattern of the predicted property EP_(T)(P) for the oil without the water. Therefore, the value of the measured property EP_(T,i,w)(M) for the oil mixed with the water is equal to the value of a predicted property EP_(T,j)(P) for the oil without the water according to the predicted profile EP_(T)(P). Apparently, the value of EP_(T,j)(P) is less than that of EP_(T,i)(P). This means that the oil which is mixed with the water acts as a dry oil which is spent more than it should be, or which has extra deterioration as compared with deterioration predicted by a predicted property EP_(T,i)(P). Therefore, a remaining usage ratio for the oil mixed with the water at the usage moment (U_(i)) is equivalent to a predicted remaining usage ratio (R_(p)) for the oil at the usage moment (U_(j)), where R_(P,j)=[EP_(T,j)(P)−EP_(T,S)]/[EP_(T,N)−EP_(T,S)]. In addition, the ratio R_(P,j) further determines the remaining usage (R_(P,j)ΔU_(F))

It will be appreciated that the predicted remaining usage ratio R_(P,i)=[EP_(T,j)(P)−EP_(T,S)]/[EP_(T,N)−EP_(T,S)] is smaller than the predicted remaining usage ratio at the moment (U_(i)), R_(P,j)=[EP_(T,i)(P)-EP_(T,S)]/[EP_(T,N)-EP_(T,S)]. This results in that the predicted remaining usage (R_(P,j)ΔU_(F)) is also less than the predicted remaining usage (R_(P,i)ΔU_(F)). However, the remaining usage (R_(P,i)ΔU_(F)) is predicted for the oil during the normal deterioration, where there is absence of the water in the oil. Therefore, it can conclude that an abnormal deterioration of the oil due to the water presence, the measured remaining usage (R_(M)ΔU_(F)) will be less than the predicted remaining usage (R_(p)ΔU_(F)) relative to the same usage moment. It will be appreciated that the above disclosure is a general conclusion, which serves to predict presence of water in the oil for any situations, as long as the sensing capacitor which is fully immersed in the mixture of the water and oil.

Thus, the present invention continually has the following steps to conclude the abnormal deterioration of the oil which occurs in the presence of the water after the prior step “m”:

(n) determining an abnormal deterioration of the oil which occurs in the presence of the water if the measured remaining usage (R_(M)ΔU_(F)) is less than the predicated remaining usage (R_(p)ΔU_(F)).

Besides the above disclosed method which applies the remaining usage to conclude the presence of the water in the oil, there is an alternative way in use of an actual remaining usage, which can also reach the same conclusion. Referring to FIG. 15, there is illustrated that the measured property EP_(T,i,W)(M) at the moment (U_(j)) due to the water presence is equal to the predicted property EP_(T,j)(P) at the moment (U_(j)). Therefore, the measured actual remaining usage for the oil mixed with water is equal to ΔU_(M)=(U_(S)−U_(j)). As a comparison, EP_(T,i)(P) represents the normal oil deterioration at the moment (U_(i)). and the predicted actual remaining usage for the oil without the water is equal to ΔU_(p)=(U_(S)−U_(i)). Apparently the measured value (ΔU_(M)) is less than the predicted value (ΔU_(p)), which also leads to the same conclusion of the abnormal deterioration of the oil which occurs in the presence of the water if the measured remaining usage is less than the predicated remaining usage. It will be appreciated that the above analysis is particularly appropriate to the situation having the non linear relationship between the properties and usages.

Now referring to FIG. 17, there is illustrated another embodiment of the present invention applying the electrical property (EP_(T)) for detecting the abnormal oil deterioration which occurs in the presence of the water. FIG. 17 illustrates an event happened during a period of the used times Δt=(t_(j)−t_(i)). The event causes inconsistency of the curves of EP_(T)(P) and EP_(T)(M), including that the measured property EP_(T,j)(M) is smaller than the predicted property EP_(T,j)(P) relative to the time moment (t_(j)). In this embodiment, the likely presence of water in the oil can be detected by comparing a rate of change of the measured property EP_(T)(M) with a rate of change of the predicted property EP_(T)(P), wherein the measured property EP_(T)(M) of the oil exhibits a faster rate towards the oil deterioration. Obviously, the rate is expressed as ΔEP_(T)/Δt. Therefore, the faster rate from the measured property indicates extra deterioration of the oil than the oil deterioration predicted by the predicted property.

It will be appreciated that an increased water amount in the oil over the time is the most likely reason to cause the above illustrated phenomenon. This could be happened if the rupture of the head gasket is big enough, which allows a large amount of the water to enter into the oil system so that the dynamic water balance in the oil cannot be maintained, as compared with the condition illustrated in FIG. 16.

In addition to situations which are illustrated in FIGS. 16 and 17, FIG. 18 illustrates an additional situation where the water could be in the oil. Referring to FIG. 18, there is illustrated measured property EP_(T,i)(M) at the time (t_(i)), which exceeds a predetermined extreme value EP_(T)(P_(E)) at the time (t_(e)) of a predicted property profile EP_(T)(P). In addition, the measured property exceeds the predetermined extreme value at a time (t_(i)) which is earlier than predicted time (t_(e)):(t_(i)<t_(e)). Of course earlier could be earlier in times, earlier in miles, etc. This too is an indication of presence of the water in the oil.

Therefore, according to the illustrations of FIGS. 16, 17 and 18 the methods for detecting the likely presence of the water in the oil comprise the claims as bellow. They follow the prior claimed step (g):

observing a likely presence of water in the oil 22 if any of the following occur:

-   -   the measured temperature compensated electrical property         EP_(T)(M) exhibits a sudden change which indicates extra         deterioration of the oil than the deterioration predicted by the         predicted property EP_(T)(P); or     -   the measured temperature compensated electrical property         EP_(T)(M) has a value which differs from the predicted property         EP_(T)(P), wherein the difference indicates extra deterioration         of the oil than the deterioration predicted by the predicted         property EP_(T)(P); or     -   the measured temperature compensated electrical property         EP_(T)(M) has a rate of change of deterioration of the oil which         differs from a rate of change of deterioration determined by the         predicted property EP_(T)(P), wherein the difference indicates         extra deterioration of the oil than the deterioration predicted         by the predicted property EP_(T)(P); or     -   the measured temperature compensated electrical property         EP_(T)(M) has a value which exceeds a predetermined extreme         value of the predicted property profile EP_(T)(P), wherein the         predetermined extreme value is exceeded at a measurement time         which is earlier than a time predicted by the predicted property         profile.

Reference to FIG. 19 illustrates a measured temperature compensated electrical property EP_(T)(M) which exhibits an initial anomaly EP_(T,i,a)(M) according to the time moment (t_(i)), and then returns to a predicted value EP_(T,j)(P) at the time moment (t_(j)). This can occur in the first few minutes (Δt) after a cold internal combustion engine is started, wherein water has condensed into the oil before the engine is started. The presence of the condensed water causes the impedance or voltage have a value which is lower than anticipated. However, after the engine has run for a short period of time, the water evaporates and the measured property EP_(T,j)(M) returns to a nominal value EP_(T,j)(P).

In this fashion an additional embodiment for detecting the presence of water in the oil, comprises;

-   -   in step (a), providing the oil 22 disposed in a crankcase of a         cold internal combustion engine;     -   starting the engine;     -   observing a likely presence of water in the oil 22 if measured         temperature compensated electrical property EP_(T)(M) in the         step (g) exhibits an initial anomaly, which indicates extra         deterioration of the oil than the deterioration predicted by the         predicted property EP_(T)(P).

The illustrations from FIGS. 16, 17, 18 and 19 disclose the abnormal oil deterioration according to the impedance or the voltage measurement. It will be appreciated that if using the current measurement, curves corresponding to the abnormal oil deterioration can be derived according to the base curve in FIG. 8.

The above discloses the first preferred embodiment of the present invention methods, which applies a dual sensor configuration including the sensing capacitor immersed in the oil, and the reference capacitor immersed in the reference oil to obtain the measured temperature compensated electrical properties of the oil. Applying the dural sensor strategy the present invention enables to quantitatively obtain the measured remaining usage of the oil as (R_(M)ΔU_(F)) or ΔU_(M). From using the measured remaining usage of the oil, the present invention further enables to differentiate the oil deterioration which occurs in the presence or absence of the water.

A variation of the above disclosed first preferred embodiment is comprised of at least two measurement sensors, as illustrated in FIG. 23. They can be affixed into specific locations of an entire lubricating oil system, such as the system of a locomotive diesel engine or ship diesel engine having a separated crankcase 34 and lubricating oil reservoir 38 which are connected by oil transporting lines 36. Therefore, the varied embodiment enables to in-situ monitor if an uneven distribution of the oil deterioration occurs through the system, particularly for detecting if there would be water accumulated in the specific locations of the system. In this embodiment of the variation, each of the at least two measurement sensors can be paired with one individual reference sensor, or the at least two measurement sensors are combined with the same reference sensor as shown in FIG. 23. Both options enable to generate the respective at least two remaining usages of the oil according to the specific locations where the at least two measurement sensors are positioned. Therefore, comparing these at least two remaining usages of the oil with the predicted remaining usage for the oil, it can conclude (1) an even distribution of the normal oil deterioration in the oil system if the at least two measured remaining usages of the oil are similar as compared with the predicted remaining usage for the oil, and (2) an uneven distribution of the oil deterioration in the oil system if the at least two measured remaining usages of the oil are dissimilar from each other as compared with the predicted remaining usage for the oil.

It will be appreciated that, in that situation (2), a further analysis can be conducted on differences including among the measured remaining usages and from different combinations of the predicted and a particular measured remaining usage. Therefore, an identification of the uneven distribution in the entire oil system is readily available and understood in accordance with the spirit and scope of the present invention methods. Therefore, such detailed analyses will not be repeated.

Now referring to FIG. 20, there is illustrated a diagram of a second apparatus for detecting deterioration in oil from the present invention. This apparatus measures the electrical property EP_(T)(M) of the capacitor C1 in the sensor 26 to represent property (EP_(T)) of the oil 22. The electrical property EP_(T)(M) is temperature compensated according to the aforementioned method, or any other desired methods, such as actually measuring the temperature of the oil and applying a compensation factor to the measured electrical property. Correspondingly, the method of the second preferred embodiment for obtaining the temperature compensated electrical property of the oil is claimed as follows:

(a) providing an oil 22 which is the oil in use, the oil is disposed in an oil system of a machine such as an oil reservoir of an machine;

(b) providing a sensor 26 which includes a capacitor (C1);

(c) positioning the sensor 26 to the oil system, wherein said capacitor (C1) is immersed in the oil;

(d) measuring a temperature compensated electrical property EP_(T)(M) of the capacitor (C1) which represents the temperature compensated electrical property (EP_(T)) of the oil, wherein said electrical property EP_(T)(M) is one of:

-   -   the impedance of the capacitor (C1);     -   the current passing through the capacitor (C1);     -   the voltage developed across the capacitor (C1);

In addition, following the above disclosed procedures which is used for obtaining the measured temperature compensated electrical property of the oil in step “d”, the second embodiment of the present invention further comprises a step (e):

(e) establishing a predicted temperature compensated electrical property profile for the oil, which reflects the normal oil deterioration, the predicted profile includes an electrical property (EP_(T,N)), which is equal to a measured property EP_(T)(M) of the oil if it is unused and dry, and another electrical property (EP_(T,S)), which is equal to the measured property EP_(T)(M) of the oil if it is spent and dry.

Once after establishing the predicted property profile EP_(T)(P), the second preferred embodiment of the present invention can apply all the same strategies thus the same claims of the first preferred embodiment, including a comparison of the measured remaining usage in the respective two forms (RΔU) and (ΔU) with the predicted remaining usage to conclude if the deterioration of the oil which occurs in the presence or absence of the water and further confirm the measured remaining usage which represents the actual remaining usage of the oil in the normal deterioration of the oil, in addition to obtain the deterioration ratio (D) of the oil Further it will be appreciated that, the second embodiment of the present invention can incorporate with the illustrations of FIGS. 16, 17, 18 and 19 for various situations where the oil deteriorates in the presence of the water. However, for a purpose to reduce the length of this application, all of the same strategies, which have been disclosed in the first preferred embodiment, will not be repeated for the disclosure of the second preferred embodiment.

It will be further appreciated that the resistance and capacitive reactance are also appropriate for the second embodiment according to the spirit and scope of the present invention.

It will be another appreciated that the second preferred embodiment further enables to comprise at least two sensors, as illustrated in FIG. 23 for the first preferred embodiment, for monitoring if there is uneven distribution of the oil deterioration through the entire lubricating oil system of the machine.

II. Method for Detecting Level of an Oil

It is well known that during operation of a machine such as the internal combustion engine, lubricating oil in use will be consumed over the time which causes amount of the oil disposed in the oil system of the machine is reduced, so as to lower a top level of the oil in the oil system. When the oil amount is reduced to be lower than a predetermined threshold amount which is usually defined by a manufacturer of the machine, moving parts of the machine can not be effectively protected. Therefore, it is necessary to have a method which can on-line detect a top level of the oil in use which is reduced to the top level of a threshold amount of the oil for protecting the machine when the oil in use is reduced.

As in the case illustrated in FIG. 9 when the measurement sensor 26 is installed on the upward wall of the crankcase 34 of the internal combustion engine, the sensing capacitor (C1) is immersed in the oil 22 and is aligned with a position 44 which correlates to the top level of the threshold amount of the oil. Therefore, reduction of the amount of the oil will lower the top level of the oil in the crankcase. When the top oil level is reduced to the top level of the threshold amount of the oil, it will cause the sensing capacitor (C1) that is not fully immersed in the oil, where its lower part is immersed in the oil and upper part is filled with the air. The fact that the sensing capacitor (C1) is partially immersed in the oil will cause a change of the electrical property of the capacitor, as compared with the property when the capacitor is fully immersed in the oil. Therefore, this situation provides the present invention an opportunity to detect the top oil levels including a top level of the threshold amount of the oil by detecting abnormal electrical properties of at least two measurement sensors, which are installed according to the respective levels of the oil.

The following first illustrates a method of the present invention for detecting the top level of the threshold amount of the oil from applying the single measurement sensor, which is illustrated in FIG. 9. The method is still based on the strategy of comparing the measured remaining usage of the oil with the predicted remaining usage for the oil.

It is well known that a plate capacitor (C), for example comprising two plates in parallel, has a capacitance described as C_(p)=∈S/d, wherein (∈) is the dielectric constant of a dielectric medium of the capacitor; (S) is an effective area of the plates, and (d) is a distance between the plates.

Now comparing a capacitance (C_(p)) of the capacitor in two conditions, (1) if it is filled with a first dielectric medium with a dielectric constant (∈₁), and (2) if it is filled with a second dielectric medium with a dielectric constant (∈₂), it can conclude that a difference between their capacitances (C_(P1)) and (C_(P2)) is proportional to the difference of the constants (∈₁) and (∈₂).

According to the above defined conditions of the capacitances (C_(P1)) and (C_(P2)) for the same capacitor, in addition to a fact that the dielectric constant ∈(a) of the air is substantially less (approximately 2-3 times) than the dielectric constant ∈(o) of the oil including the mineral oil and silicon oil (this information can be found elsewhere including from the website: clippercontrol having a “.com” suffix), therefore, the capacitance (C_(P2)) of the capacitor filled with the air is less than the capacitance (C_(P1)) of the same capacitor filled with the oil. It can further conclude that, the impedance (Z₂) of the capacitor filled with the air is bigger than the impedance (Z₁) of the same capacitor filled with the oil, the voltage (V₂) is also bigger than the voltage (V_(i)) if the constant current measurement is applied, and the current (I₂) is smaller than the current (I₁) if a constant voltage measurement is applied.

Now comparing a capacitance (C_(p)) of the capacitor in another two situations, (1) a part of the capacitor is filled with the air and the rest of the capacitor is filled with the oil, and (2) the same capacitor is fully filled with the oil.

In the first situation when the part of the capacitor is filled with air and the rest part is filled with oil, the capacitance (C_(P1)) is a summation of a capacitance of the air: C_(P1)(a)=∈(a) S_(a)/d and a capacitance of the oil: C_(P1)(o)=∈(o) S_(o)/d, wherein (S_(a)) is an effective plate area which is occupied by the air, and (S_(o)) is the area which is occupied by the oil, and S=(S_(a)+S_(o)).

If comparing the capacitance (C_(P1)) of the capacitor filled with the air and oil in the first situation with the capacitance (C_(P2)) of the same capacitor fully filled with the oil in the second situation, a ratio of C_(P1)/C_(P2) is equal to [∈(a) S_(a)/d+∈(o) S_(o)/d]/∈(o)S/d. The ratio can be simplified as: C_(P1)/C_(P2)=[∈(a) S_(a)+∈(o) S_(O)]/∈(o)S. Through a mathematic transformation, the simplified ratio is equal to: 1-[∈(o)-∈(a)] S_(a)/S, which has a value of less than a unity 1.

The above analysis demonstrates that the capacitance (C_(P1)) of the capacitor whose a part filled with the air and the rest filled with the oil is less than the capacitance (C_(P2)) of the same capacitor which is fully filled with the oil.

It will be appreciated that, from the above conclusion, one can derive that the impedance (Z₁) of the capacitor having the capacitance (C_(P1)) is bigger than the impedance (Z₂) of the same capacitor having the capacitance (C_(P2)). Accordingly, the voltage (V₁) is higher than the voltage (V₂) if applying a constant current measurement, and the current (I₁) is smaller than the current (I₂) if applying a constant voltage measurement. Therefore, the electrical property of the capacitor filled with the oil and air will provide a false phenomenon less deterioration of the oil, as compared with the oil deterioration determined by the same capacitor which is fully filled withe the oil.

Having the above conclusions in mind and referring to FIGS. 21 and 22 now, there is illustrated how an oil reduction to the threshold amount of the oil causes a change of the measured temperature compensated electrical property and the remaining usage of the oil as well from the present invention. FIG. 21 illustrates a part of the measured temperature compensated profile EP_(T)(M), and the predicted property profile EP_(T)(P) which includes the value (EP_(T,N)) and (EP_(T,S)) to correspond the respective usage (U_(N)) and (U_(S)). The predicted profile is the same one as that illustrated in FIG. 14.

As illustrated, up to a moment (U_(i)) the measured property EP_(T,i)(M) is consistent with the predicted property EP_(T,i)(P). However, staring from the moment “U_(i)”, the measured property differs from the predicted property due to the amount of the oil which is reduced to the threshold amount. Therefore, the top level of the oil is lowered to reach the top level of the threshold amount of the oil, which is aligned with the position 44, as illustrated in FIG. 9. In this situation, an upper part of the sensing capacitor (C1) is filled with the air.

It will be appreciated that there are various situations which cause the sensing capacitor that is not fully immersed in the oil. However they can be always classified to a first situation: (1) a gradually losing the oil, such as extra consumption of the oil according to an intensive usage of the machine, and a second situation: (2) a significantly losing the oil in a short period of the time, such as an oil leaking of the crankcase. Referring to FIG. 21, there is illustrated the measured properties EP_(T,q)(M1) and EP_(T)(M2) according to the respective described first and second situations (1) and (2).

As illustrated in FIG. 21, in the first situation of the gradually losing the oil, the measured property EP_(T,q)(M1) behaves a corresponded graduate departure from the predicted property profile EP_(T)(P). For example an impedance or a voltage of the sensing capacitor is increasingly larger than the corresponding predicted value. In contrast, in the second situation of the quickly losing the oil, the measured property EP_(T)(M2) exhibits a sudden change during a small interval of the usage. Accordingly, the sensing capacitor also suffers a significant loss of the oil, which makes the measured property change dramatically towards a direction of less oil deterioration. For example, the impedance or voltage exhibits a sudden and dramatic increase of the value. It will be appreciated that the first situation (1) represents the most probable situations, where occur that a top level of the oil is reduced to the top level of the threshold amount of the oil. Thus, FIG. 22 particularly illustrates the situation, from which a conclusion can be conducted for determining the threshold amount of the oil from detecting the corresponded top oil level. This conclusion can also be applied to the second situation (2).

FIG. 22 magnifies part of the profiles starting at the moment (U_(i)), when the measured property EP_(T)(M1) departs from the predicted one. After a short usage period from the moment (U_(i)) to moment (U_(q)), the measured property exhibits a value of EP_(T,q)(M1) at the moment (U_(q)), which is higher than a predicted value of EP_(T,q)(P). EP_(T,q)(P) represents the normal consumption of the oil according to the moment (U_(q)). Moreover, in this situation the measured value of EP_(T,q)(M1) is equal to a predicted value of EP_(T,k)(P) which correlates to the moment (U_(k)). Obviously, the moment (U_(k)) happens earlier that the moment (U_(q)).

Therefore, the measured property at the moment (U_(q)) has a measured remaining usage ratio, which is equal to a predicted remaining usage ratio at the moment (U_(k)): R_(k)=[EP_(T,k)(P)−EP_(T,S)]/[EP_(T,N)−EP_(T,S)]. The usage ratio (R_(k)) further determines the remaining usage (R_(k)ΔU_(F))=R_(k)×(U_(S)−U_(N)). Therefore, a measured remaining usage according to the measured property EP_(T,q)(M1) is equal to the predicted remaining usage (R_(k)ΔU_(F)).

Apparently, the predicted remaining usage ratio R_(k) is larger than the predicted remaining usage ratio: R_(q)=[EP_(T,q)(P)−EP_(T,S)]/[EP_(T,N)−EP_(T,S)], where (R_(q)) correlates to the physical condition that there is a sufficient amount of the oil that is dry in the oil reservoir, which makes the sensing capacitor (C1) fully immersed in the oil. This situation also results in that the remaining usage (R_(k)ΔU_(F)) is larger than the remaining usage (R_(q)ΔU_(F)). Therefore, the above analysis' concludes: the measured remaining usage which is equivalent to (R_(k)ΔU_(F)) is apparently larger than the predicted one (R_(q)ΔU_(F)), wherein the predicted one represents the situation that the sensing capacitor is fully immersed in the oil which has a sufficient amount so that the top oil level is higher than the level of the threshold amount of the oil.

Consequently, a claim step (o) can be made: determining a top level of the oil which is reduced to the top level of a predetermined threshold amount of the oil if the measured remaining usage (R_(M)ΔU_(F)) is larger than the predicted remaining usage (R_(p)ΔU_(F)) according to a same usage moment. Obviously, the usage can be the used times or traveled miles.

It will be appreciated that the above is a general conclusion for all situations including the situation (2) where the insufficient amount of the oil also happens.

It will be further appreciated that, there is an alternative way which can conduct the same conclusion as claimed in step (o). Referring to FIGS. 21 and 22, there is illustrated that (U_(q)) corresponds to the predicted EP_(T,q)(P). Therefore, the predict actual remaining usage is (ΔU_(p))=ΔU_(q)=(U_(s)−U_(q)). However, the measured property EP_(T,q)(M1) is equal to the predicted property EP_(T,k)(P), which corresponds to (U_(k)). Therefore, the measured actual remaining usage (ΔU_(M)) is equivalent to the predicted actual remaining usage ΔU_(k)=(U_(S)−U_(k)). Apparently, the measured actual remaining usage (ΔU_(k)) is larger than the predicated actual remaining usage (ΔU_(q)). This leads to the same conclusion of reaching the top level of the threshold amount of the oil during the oil reduction. Therefore, despite of the shape of the temperature compensated profile, the embodiment of the present invention enables to diagnose if it reaches the top level of the threshold amount of the oil during the progress of the oil reduction.

In addition to application of the remaining usage of the oil, the measured temperature compensated electrical property EP_(T)(M) also can be used to predict that the top oil level is reduced to the top level of the threshold amount of the oil according to the illustrations of FIGS. 21 and 22. As illustrated in the case caused by the first situation (1), the measured property EP_(T,q)(M1) differs to the predicted property EP_(T,q)(P). However, their difference indicates less oil deterioration of the measured property than the deterioration determined by the predicted property. Therefore, the present invention can further claims as:

-   -   predicting the top level of the oil which is reduced to the top         level of the threshold amount of the oil if the measured         temperature compensated electrical property differs to the         predicted property wherein the difference indicates less         deterioration of the oil than the deterioration determined by         the predicted electrical property.

It will be appreciated that the illustrated curves for the electrical property in FIGS. 21 and 22 is one of the impedance or voltage. If the measured property is the current, the curve would be as that shown in FIG. 8. In addition, the electrical property could be one of the components of the impedance, resistance or reactance, rather than the total composite impedance.

Referring to FIG. 24, a variation of the above disclosed embodiment is to apply at least two measurement sensors 26 positioned along a vertical orientation to monitor change of a full scale of the oil top level of the crankcase 34. For example, in this embodiment, the first of the at least two sensors is positioned on the upward wall of the oil reservoir 34, wherein its sensing capacitor is aligned with a position 40. The position is adjacent but below the initial top oil level when a full amount of the oil is just newly disposed in the oil reservoir. The second of the at least two sensors is installed wherein its sensing capacitor is positioned aligning with the top level of the threshold amount of the oil 42. Therefore, the respective capacitor of each of the at least two measurement sensors will provide the respective information on the oil level starting the full level of the oil, which then drops to the level of the threshold amount of the oil. The user of the machine can then take appropriate actions to protect the machine from damage. In addition, a third of the at least two measurement sensors can also be installed to a level which is even lower, as compared with the top level of the threshold amount of the oil. In this embodiment, each of the at least two measurement sensors can be combined with one individual reference sensor, or the at least two sensors can be combined with the same one reference sensor 28 shown in FIG. 24, or several of the at least two sensors are combined with a reference sensor. All of these variations are within the spirit and scope of the present invention.

It will be appreciated that the above disclosed embodiment for predicting the top level of the threshold amount of the oil can also be applied to the second preferred embodiment illustrated in FIG. 20, where the sensing capacitor (C1) is aligned with the top level 44 of the threshold amount of the oil. It will be additionally appreciated that the second preferred embodiment also enables to detect a full level of the oil from applying at least two measurement sensors, which has been illustrated in FIG. 24 for the first preferred embodiment. Therefore, a disclosure of this embodiment will not repeated again.

It will be further appreciated that there is a very small probability that two events happen simultaneously when a large amount of the water enters into the oil and the oil significantly leaks from the reservoir. Therefore, the present invention excludes discussions of this situation which occurs in the very small probability, and which can also be classified accordingly following the spirit and scope of the present invention.

Of course the present invention is not intended to be restricted to any particular form or arrangement, or any specific embodiment, or any specific use, disclosed herein, since the same may be modified in various particulars or relations without departing from the spirit or scope of the claimed invention hereinabove shown and described of which the apparatus or method shown is intended only for illustration and disclosure of an operative embodiment and not to show all of the various forms or modifications in which this invention might be embodied or operated. 

1. A method for detecting oil deterioration and oil level, comprising the steps of: a. providing an oil in use, said oil in use is placed in an oil system of a machine; b. providing a reference oil being free of water, said reference oil is disposed in a sealed container which is located in a common temperature environment with said oil; c. providing a measurement sensor which includes a first capacitor; d. providing a reference sensor which includes a second capacitor, said second capacitor is immersed in said reference oil; e. positioning said measurement sensor wherein said first capacitor is immersed in said oil in use; f. measuring an electrical property of said first capacitor and an electrical property of said second capacitor, wherein said electrical property is one of: an impedance of the respective said first and said second capacitors; a current passing through the respective said first and said second capacitors; a voltage developed across the respective said first and said second capacitors; g. combining said electrical property of said first capacitor with said electrical property of said second capacitor to obtain a measured temperature compensated electrical property of said first capacitor, which represents a measured temperature compensated electrical property EP_(T)(M) of said oil in use; h. following the steps (a) to (g) establishing a predicted temperature compensated electrical property profile for said oil, which reflects a normal oil deterioration for said oil, said predicted profile includes an electrical property (EP_(T,N)), which is equal to a measured property EP_(T)(M) of said oil if it is unused and dry, and another electrical property (EP_(T,S)), which is equal to the measured property EP_(T)(M) of said oil if it is spent and dry; i. establishing a full range of usage of said oil as ΔU_(F)=(U_(S)−U_(N)) according to change of said electrical properties (EP_(T,N)−EP_(T,S)), wherein U represents an actual oil usage which is an independent variable to said property EP_(T); said U_(N) is an actual usage of said unused oil and said U_(S) is an actual usage of said spent oil; j. defining a measured normalized remaining usage ratio R_(M) of said oil having said property EP_(T)(M) as: R_(M)=[EP_(T)(M)−EP_(T,S)]/[EP_(T,N)−EP_(T,S)], wherein R is a remaining usage ratio and ranges from one for said unused oil to zero for said spent oil; k. defining a measured remaining usage of said oil as (R_(M)ΔU_(F)); l. from said predicted property profile, determining a predicted temperature compensated electrical property EP_(T)(P) according to a same usage moment as compared with said measured property EP_(T)(M), establishing a predicated remaining usage ratio as R_(p)=[EP_(T)(P)-EP_(T,S)]/[EP_(T,N)-EP_(T,S)], from which to obtain a predicted remaining usage (R_(p)ΔU_(F)); m. determining said normal deterioration of said oil which occurs in the absence of said water if said measured remaining usage (R_(M)ΔU_(F)) is similar to said predicated remaining usage (R_(p)ΔU_(F)), and confirming said measured remaining usage which represents an actual remaining usage of said oil; n. determining an abnormal deterioration of said oil which occurs in the presence of said water if said measured remaining usage (R_(M)ΔU_(F)) is less than said predicted remaining usage (R_(p)ΔU_(F)); and o. determining a top level of said oil which is reduced to a top level of a predetermined threshold amount of said oil if said measured remaining usage (R_(M)ΔU_(F)) is larger than said predicted remaining usage (R_(p)ΔU_(F)).
 2. The method in accordance with claim 1 in step “b”, wherein said reference oil is one of said unused oil, or a partially spent oil, or said spent oil, and said reference oil has a similar thermal property as compared with a thermal property of sais oil.
 3. The method in accordance with claim 1 in step “d”, wherein said first capacitor and second capacitor have structural relationships which make said capacitors exhibit a same change of the respective said electrical properties as a function of oil temperature change when said first capacitor and said second capacitor are immersed in a same oil;
 4. The method in accordance with claim 1 in step “f”, further comprising: said electrical property is a resistance or a capacitive reactance of the respective said first capacitor and said second capacitor.
 5. The method in accordance with claim 1 in step “i”, wherein said usage is a number of used times or traveled miles.
 6. The method in accordance with claim 1 in step “g”, further comprising: observing a likely presence of said water in said oil if said measured temperature compensated electrical property EP_(T)(M) occurring any of the following: said measured property EP_(T)(M) exhibits a sudden change, wherein said sudden change indicates extra deterioration of said oil than deterioration predicted by said predicted temperature compensated electrical property EP_(T)(P); or said measured property EP_(T)(M) having a value which differs from said predicted property EP_(T)(P), wherein said difference indicates extra deterioration of said oil than deterioration predicted by said predicted property EP_(T)(P); or said measured temperature compensated electrical property EP_(T)(M) has a rate of change of deterioration of said oil which differs from a rate of change of deterioration determined by said predicted property EP_(T)(P), wherein said difference indicates extra deterioration of said oil than the deterioration predicted by said predicted property EP_(T)(P); or said measured property EP_(T)(M) having a value which exceeds a predetermined extreme value of said predicted property profile, wherein said predetermined extreme value is exceeded at a measurement time which is earlier than a time predicted by said predicted property EP_(T)(P).
 7. The method in accordance with claim 1 in step (a), further comprising: positioning said oil in a cold internal combustion engine, starting said engine, and observing a likely presence of said water in said oil if said measured property EP_(T)(M) of step “g” exhibits an initial anomaly, wherein said initial anomaly indicates extra deterioration of said oil than deterioration predicted by said predicted property EP_(T)(P).
 8. The method in accordance with claim 1 in step “k”, further comprising the following steps: p. determining a measured actual remaining usage of said oil as ΔU_(M)=(U_(S)−U_(M)), wherein said U_(M) is corresponding to said measured property EP_(T)(M); q. defining a predicted actual remaining usage as Δ U_(p)=U_(S)−U_(p) for said oil, wherein said U_(p) correlates to said predicted property EP_(T)(P); r. determining said normal deterioration of said oil which occurs in the absence of said water if said measured actual remaining usage ΔU_(M) is similar to said predicted actual remaining usage ΔU_(p), and confirming said measured actual remaining usage; S. determining said abnormal deterioration fo said oil which occurs in the presence of said water if said measured actual remaining usage ΔU_(M) is less than said predicted actual remaining usage ΔU_(p); and t. determining said top level of said oil which is reduced to said top level of said predetermined threshold amount of said oil if said measured actual remaining usage ΔU_(M) is larger than said predicted actual remaining usage ΔU_(p).
 9. The method in accordance with claim 1 in step “j”, further comprising a measured deterioration degree D_(M) for said oil having said property of EP_(T)(M) as: D _(M)=[EP_(T,N)−EP_(T)(M)]/[EP_(T,N)−EP_(T,S)], wherein D is normalized ranging from zero for said unused oil to one for said spent oil.
 10. The method in accordance with claim 1 in step “e”, further comprising: placing said measurement sensor in said oil system wherein said first capacitor is positioned aligning with said top level of the threshold amount of said oil of said oil system.
 11. The method in accordance with claim 1 in step “h”, further comprising: predicting said top level of the oil which is reduced to said top level of the threshold amount of the oil if said measured temperature compensated electrical property differs to said predicted property wherein said difference indicates less deterioration of the oil than deterioration determined by said predicted electrical property.
 12. The method in accordance with claim 1 in step “c”, further comprising at least two said measurement sensors, each of which comprises a respective first capacitor that is immersed in said oil, said at least two measurement sensor are placed at the respective at least two different locations of said oil system of said machine.
 13. The method in accordance with claim 12, wherein a first of said at least two measurement sensors is positioned in said oil system, wherein its said first capacitor is aligned with a level adjacent but below an initial top oil level when a full amount of said oil is just newly disposed in said oil system, a second of said at least two sensors is installed wherein its said first capacitor is positioned aligning with said top level of said threshold amount of said oil.
 14. A method for detecting oil deterioration and oil level, comprising the steps of a. providing an oil in use, said oil in use is placed in an oil system of a machine; b. providing a sensor which includes a capacitor; c. positioning said sensor wherein said capacitor is immersed in said oil; d. measuring a temperature compensated electrical property of said capacitor, which represents a measured temperature compensated electrical property EP_(T)(M) of said oil in use, wherein said electrical property is one of: an impedance of said capacitor; a current passing through said capacitor; a voltage developed across said capacitor; e. establishing a predicted temperature compensated electrical property profile for said oil, which reflects a normal oil deterioration for said oil, said predicted profile includes an electrical property (EP_(T,N)), which is equal to a measured property EP_(T)(M) of said oil if it is unused and dry, and another electrical property (EP_(T,S)), which is equal to the measured property EP_(T)(M) of said oil if it is spent and dry; f. establishing a full range of usage of said oil as ΔU_(F)=(U_(S)−U_(N)) according to change of said electrical properties (EP_(T,N)−EP_(T,S)), wherein U represents an actual oil usage which is an independent variable to said property EP_(T); said U_(N) is an actual usage of said unused oil and said U_(s) is an actual usage of said spent oil; g. defining a measured normalized remaining usage ratio R_(M) of said oil having said property EP_(T)(M) as: R _(M)=[EP_(T)(M)−EP_(T,S)]/[EP_(T,N)−EP_(T,S)], wherein R is a remaining usage and ranges from one for said unused oil to zero for said spent oil; h. defining a measured remaining usage of said oil as (R_(M) ΔU_(F)); i. from said predicted property profile, determining a predicted temperature compensated electrical property EP_(T)(P) according to a same usage moment as compared with said measured property EP_(T)(M), establishing a predicated remaining usage ratio as R_(p)=[EP_(T)(P)−EP_(T,S)]/[EP_(T,N)−EP_(T,S)], from which to obtain a predicted remaining usage (R_(p)ΔU_(F)); j. determining said normal deterioration of said oil which occurs in the absence of said water if said measured remaining usage (R_(M)ΔU_(F)) is similar to said predicated remaining usage (R_(p)ΔU_(F)), and confirming said measured remaining usage which represents an actual remaining usage of said oil; k. determining an abnormal deterioration of said oil which occurs in the presence of said water if said measured remaining usage (R_(M l ΔU) _(F)) is less than said predicted remaining usage (R_(p)ΔU_(F)); and l. determining a top level of said oil which is reduced to a top level of a predetermined threshold amount of said oil if said measured remaining usage (R_(M)ΔU_(F)) is larger than said predicted remaining usage (R_(p)ΔU_(F)).
 15. The method in accordance with claim 14 in step “d”, further comprising: said electrical property is a resistance or a capacitive reactance of the respective said first capacitor and said second capacitor.
 16. The method in accordance with claim 14 in step “f”, wherein said usage is a number of used times or traveled miles.
 17. The method in accordance with claim 14 in step “d”, further comprising: observing a likely presence of said water in said oil if said measured temperature compensated electrical property EP_(T)(M) occurring any of the following: said measured property EP_(T)(M) exhibits a sudden change, wherein said sudden change indicates extra deterioration of said oil than deterioration predicted by said predicted temperature compensated electrical property EP_(T)(P); or said measured property EP_(T)(M) having a value which differs from said predicted property EP_(T)(P), wherein said difference indicates extra deterioration of said oil than deterioration predicted by said predicted property EP_(T)(P); or said measured temperature compensated electrical property EP_(T)(M) has a rate of change of deterioration of said oil which differs from a rate of change of deterioration determined by said predicted property EP_(T)(P), wherein said difference indicates extra deterioration of said oil than the deterioration predicted by said predicted property EP_(T)(P); or said measured property EP_(T)(M) having a value which exceeds a predetermined extreme value of said predicted property profile, wherein said predetermined extreme value is exceeded at a measurement time which is earlier than a time predicted by said predicted property EP_(T)(P).
 18. The method in accordance with claim 14 in step (a), further comprising: positioning said oil in a cold internal combustion engine, starting said engine, and observing a likely presence of said water in said oil if said measured property EP_(T)(M) of step “g” exhibits an initial anomaly, wherein said initial anomaly indicates extra deterioration of said oil than deterioration predicted by said predicted property EP_(T)(P).
 19. The method in accordance with claim 14 in step “g”, further comprising the following steps: m. determining a measured actual remaining usage of said oil as ΔU_(M)=(U_(S)−U_(M)), wherein said U_(M) is corresponding to said measured property EP_(T)(M); n. defining a predicted actual remaining usage as Δ U_(p)=U_(S)−U_(p) for said oil, wherein said U_(p) correlates to said predicted property EP_(T)(P); o. determining said normal deterioration of said oil which occurs in the absence of said water if said measured actual remaining usage ΔU_(M) is similar to said predicted actual remaining usage ΔU_(p), and confirming said measured actual remaining usage; p. determining said abnormal deterioration fo said oil which occurs in the presence of said water if said measured actual remaining usage ΔU_(M) is less than said predicted actual remaining usage ΔU_(p); and q. determining said top level of said oil which is reduced to said top level of said predetermined threshold amount of said oil if said measured actual remaining usage ΔU_(M) is larger than said predicted actual remaining usage ΔU_(p).
 20. The method in accordance with claim 14 in step “g”, further comprising a measured deterioration degree D_(M) for said oil having said property of EP_(T)(M) as: D _(M)=[EP_(T,N)−EP_(T)(M)]/[EP_(T,N)−EP_(T,S)], wherein D is normalized ranging from zero for said unused oil to one for said spent oil.
 21. The method in accordance with claim 14 in step “c”, further comprising: placing said sensor in said oil system wherein said capacitor is positioned aligning with said top level of the threshold amount of said oil in said oil system.
 22. The method in accordance with claim 14 in step “e”, further comprising: predicting said top level of the oil which is reduced to said top level of the threshold amount of the oil if said measured temperature compensated electrical property differs to said predicted property wherein said difference indicates less deterioration of the oil than deterioration determined by said predicted electrical property.
 23. The method in accordance with claim 14 in step “b”, further comprising at least two said sensors, each of which comprises a respective capacitor that is immersed in said oil, said at least two sensors are placed at the respective at least two different locations of said oil system of said machine.
 24. The method in accordance with claim 23, wherein a first of said at least two sensors is positioned in said oil system, wherein its said capacitor is aligned with a level adjacent but below an initial top oil level when a full amount of said oil is just newly disposed in said oil system, a second of said at least two sensors is installed wherein its said capacitor is positioned aligning with said top level of said threshold amount of said oil.
 25. A method for detecting oil deterioration of an oil system of a machine including steps of applying a measurement sensor having a first capacitor immersed in an oil in use and a reference sensor having a second capacitor immersed in a reference oil; measuring one of electrical properties of the respective first and second capacitors; combining the electrical properties of the respective first and second capacitors to obtain a temperature compensated electrical property of the first capacitor which represents a temperature compensated electrical property of the oil in use; establishing a predicted property file including a predicted property as compared with the measured property, establishing a measured remaining usage ratio which leads to a measured remaining usage of the oil in use, and defining a predicted remaining usage ratio for the oil which further leads to a predicted remaining usage for the oil in use, further comprising the steps of: a. providing at least two measurement sensors, including a first of said at least two measurement sensors having a first capacitor immersed in said oil in use and a second of said at least two measurement sensors having a first capacitor immersed in said oil in use; b. positioning said first and said second of said at least two measurement sensors in different locations of said oil system, therefore, each of said first capacitor of the respective said first and said second of said at least two measurement sensors obtaining the respective measured remaining usages of said oil located at the respective said locations of said oil system; c. determining an even distribution of a normal oil deterioration of said oil which occurs in the absence of water in said oil system if the respective said measured remaining usages from the respective first and second of said at least two measurement sensors are similar to said predicted remaining usage, and confirming one of the respective said measured remaining usage as an actual remaining usage of said oil in said oil system; and d. determining an uneven distribution of oil deterioration in said oil system if the respective said measured remaining usages form the respective said first and said second of said at least two measurement sensors are different from each other, as compared with said predicted remaining usage. 